JPH0620815A - Manufacture of rare earth bonded magnet - Google Patents

Abstract

PURPOSE:To enhance coercive force and to improve long-term reliability by a method wherein low melting point metal powder is added to the alloy powder, having specific particle diameter and the compound of specific crystal structure as the main phase, which is mainly composed of rare earth metal, Fe and N. CONSTITUTION:This manufacturing method is the method in which rare earth bonded magnet is formed as follows: metal powder, consisting of at least a kind selected from Sn, Zn, Pb, In, Al and Mg, is mixed into alloy powder of 20 to 150mum in average particle diameter having rare earth metal, Fe and N as the main component, and also having a Th2Zn17 or ThMn12 type crystal structure compound as the main phase. After the above-mentioned mixed powder has been compression-molded, a heat treatment is conducted in the temperature range of 100 to 600 deg.C. As a result, sufficient coercive force can be ensured even when coarse powder is used, and a rare earth bonded magnet, having excellent long-term reliability, can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rare earth metal (R) -F.
The present invention relates to a method for manufacturing an eN bond magnet, and more particularly to a method for manufacturing a bond magnet with improved mass productivity and long-term stability by using coarse powder.

[0002]

2. Description of the Related Art In recent years, high-performance Nd-Fe-B system permanent magnets have been widely used with the miniaturization of various electronic devices. However, since this magnet has a low Curie point of about 310 ° C, it has poor temperature characteristics and is difficult to use above 150 ° C.

On the other hand, by introducing nitrogen into an alloy of a rare earth metal and iron, for example, an Sm-Fe-N-H-based alloy having a compound having a Th ₂ Zn ₁₇ type crystal structure as a main phase has excellent magnetic properties. And a Curie point of about 470 ° C. Further, it has been proposed that an Nd-Fe-Ti-N-based alloy containing a compound having a Th Mn ₁₂ type crystal structure as a main phase also has similar magnetism.

[0004]

However, the above-mentioned R
The -Fe-N-based alloy cannot obtain the coercive force required as a permanent magnet unless it is finely pulverized to a particle size of several μm, and since this fine powder is used, the formability deteriorates and high-pressure forming becomes necessary. As a result, the mold life is shortened, and moreover, it easily oxidizes under high temperature and high humidity, so that there is a problem that the bond magnet lacks long-term reliability.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to secure a sufficient coercive force even if a coarse powder is used, and thus a method for producing a rare earth bonded magnet excellent in manufacturability and long-term reliability. The purpose is to provide.

[0006]

[Means for Solving the Problems] In order to solve the above problems,
The present invention provides an alloy powder having a rare earth metal (R), Fe and N as main components and a compound having a Th ₂ Zn ₁₇ or Th Mn ₁₂ type crystal structure as a main phase and an average particle size of 20 to 150 μm.
It is characterized in that metal powder consisting of at least one of Sn, Zn, Pb, In, Al and Mg is mixed in an amount of 3 to 30% by weight, the mixed powder is compression-molded and then heat-treated at a temperature range of 100 to 600 ° C. And

In the present invention, as the R-Fe-N-based alloy, a Sm ₂ Fe ₁₇ Nx composition having a Th ₂ Zn ₁₇ type crystal structure as a main phase or a Th Mn ₁₂ type crystal structure as a main phase is mainly used. Typical examples are Nd (Fe, M) ₁₂ Nx composition and Pr (Fe, M) ₁₂ Nx composition as a phase (here, M means fiber metal). In this case, the content of N is selected to be several to 20 several atomic%. In these alloys, a part of Fe can be replaced with another transition metal such as Co or Ti, or two or more kinds of rare earth metals can be used as the rare earth metal. These alloys have greatly increased saturation magnetic flux density, crystal magnetic anisotropy and Curie point, and are excellent as permanent magnet materials. In particular, Co is effective in raising the Curie point and improving the corrosion resistance. Also, good magnetic characteristics can be obtained by replacing the nitrogen with carbon.

In the present invention, the method of obtaining the alloy powder is arbitrary, and for example, a method of obtaining a mother alloy powder of a rare earth metal and Fe (and optionally other metal) and injecting N into this is used. it can. In this case, as a method for obtaining the mother alloy powder, a raw material in which a rare earth metal and Fe (and optionally other metal) are blended in a predetermined ratio is subjected to high frequency melting, and the molten alloy is poured into a mold to temporarily alloy ingot. After performing homogenization at high temperature, it is possible to use a method such as jaw crusher, stamp mill, ball mill, etc., to obtain powder of desired particle size, or a method of rapidly cooling molten alloy directly to powder. it can.

The penetration of N into the mother alloy powder can be carried out by bringing the mother alloy powder into contact with a nitriding gas such as nitrogen, ammonia, or a mixed gas of nitrogen and hydrogen at a high temperature. In this case, the nitriding temperature is
If the temperature is less than 200 ° C, the penetration of N is insufficient, and if it exceeds 600 ° C, the predetermined alloy compound phase is easily decomposed.
It is desirable to select the range of 600 ° C. Further, by performing the nitriding treatment under a high pressure of several tens of atmospheres, nitriding of the mother alloy powder can be promoted. Further, it is possible to pulverize again after the nitriding treatment to adjust the powder particle size and magnetic characteristics.

In the present invention, the grain size of the alloy powder is 20 μm.
If it is less than m, it is not preferable for mass production because it requires high-pressure molding when it is made into a bonded magnet, and it easily oxidizes in the manufacturing process. On the other hand, if it exceeds 150 μm, nitrogen is not sufficiently penetrated. The range was up to 150 μm.

In the present invention, as the metal powder to be mixed with the obtained alloy powder, Sn, Zn and P which are low melting point metals are used.
At least one of b, In, Al, and Mg is selected because these metals function as binders for bond magnets, and also have a function of partially reacting with alloy powder by heat treatment described later to increase coercive force. Because there is. If the amount of these mixed metals is less than 3% by weight, the bonding strength as a magnet is insufficient, and if it exceeds 30% by weight, the magnetic properties are greatly deteriorated. Therefore, the addition amount is set to 3 to 30% by weight.

Further, the present invention is characterized in that the magnetic properties (coercive force) and the bond strength are improved by heat treatment after compression molding. No improvement was observed, and when the temperature exceeds 600 ° C, the compound is decomposed and the magnetic properties deteriorate, so this was set to 100 to 600 ° C. It is desirable that this heat treatment be performed in an inert gas atmosphere or in a vacuum. Further, by performing the compression molding at 100 to 600 ° C., the subsequent heat treatment can be omitted. Further, the molded body after the heat treatment is impregnated with an organic resin for improving the strength. Alternatively, it is also effective to form an organic or inorganic film for improving the corrosion resistance.

[0013]

In the rare earth bonded magnet having the above-mentioned structure, the addition of the low melting point metal or alloy to the alloy powder and the subsequent heat treatment increase the magnetic properties, especially the coercive force, which makes it possible to use the coarse powder. Become.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1 Samarium having a purity of 99.9% and electrolytic iron were blended in a predetermined ratio, and high frequency melting was performed to produce an alloy ingot of Sm ₂ Fe ₁₇ composition having a Th ₂ Zn ₁₇ type crystal structure as a main phase. This ingot was homogenized at 1200 ° C. for 12 hours in an Ar gas atmosphere, and various mother alloy powders having an average particle size of 5 to 180 μm were obtained by a stamp mill and a ball mill. next,
This alloy powder is heated at 450 ° C for 2 to 24 in nitrogen gas at 5 atm.
The alloy powder (nitriding powder) was obtained by holding for a period of time and infiltrating N. Subsequently, 10% by weight of Zn powder having a particle size of 5 μm was added to these nitride powders and mixed by a ball mill, and the mixed powder was compression molded at a pressure of 5 Ton / cm ² while applying a magnetic field of 15 kOe. . Then, the molded body was charged into an electric furnace and heat-treated at 400 ° C. for 6 hours in an argon gas atmosphere to obtain a plurality of magnet body samples. The crystal structure of the obtained magnet sample was confirmed by an X-ray diffraction method, and the magnetic characteristics were measured by a BH tracer. On the other hand, in order to know the long-term stability of the nitriding powder, the weight change of the powder was measured by keeping it in a thermostat at 125 ° C. for 500 hours.

FIG. 1 shows the effect of the average grain size of the alloy powder on the maximum magnetic energy product BHmax, the coercive force iHc and the residual magnetic flux density Br of the magnet sample. Figure 1
Therefore, the maximum magnetic energy product BHmax and the residual magnetic flux density B
Although r has a peak at an average powder particle size of 25 μm, it has a high value in the average powder particle size range of 20 to 150 μm, and coercive force iHc increases as the nitride powder particle size decreases according to the single domain particle theory. There is.

FIG. 2 shows the effects of the average powder particle size and the holding time on the increase in the oxidized weight of the nitride powder. Figure 2
From the above, it is shown that the larger the particle size of the nitriding powder, the smaller the weight increase rate due to oxidation and the more excellent long-term stability.

Example 2 Nitride powder having an Sm ₂ Fe ₁₇ N ₃ composition and an average particle size of 5 to 180 μm prepared in Example 1 was mixed with Sn, Zn, Pb, In, Al, Mg, as a mixed metal (metal binder). C
u or their alloy was added by 10% by weight, and mixed and shaped in the same manner as in Example 1. Then, this molded body was charged into an electric furnace and heat-treated at a predetermined temperature for 2 hours in an argon gas atmosphere to manufacture magnet samples 1 to 7, which were manufactured in Example 1.
It was subjected to the same measurement test of magnetic properties as in. For comparison, a magnet sample 8 containing no metal binder was manufactured and was also subjected to the same magnetic characteristic measurement test. The results are shown in Table 1. In addition, the numerical value of the mixed metal in Table 1 is% by weight.
Is represented. The symbol * in the table indicates the comparative material.

[0019]

[Table 1]

As is clear from Table 1, all the magnet samples 1 to 6 according to the present invention have a residual magnetic flux density Br and a coercive force.
High values were obtained for both iHc, and it became clear that the use of so-called low melting point metals and alloys specified in the present invention was effective in improving the magnetic properties. On the other hand, the comparative sample 7 was inferior to the magnet sample according to the present invention in magnetic characteristics, and it was found that Cu was not suitable as a binder for magnets. Further, the sample of Comparative Example 8 has a low strength because it does not use a metal binder, and has a low coercive force iHc.

Example 3 1 to 40% by weight of Zn powder having a particle size of 5 μm was added to the nitride powder having an average particle size of 25 μm manufactured in Example 1 and mixed by a ball mill. This mixed powder was compression-molded at a pressure of 7 ton / cm ² while applying a magnetic field of 15 kOe, and this molded body was placed in an electric furnace and placed in an argon gas atmosphere for 500
Heat treatment was performed at 1 ° C. for 1 hour to manufacture magnet body samples 11 to 17, and these were subjected to the same magnetic characteristic measurement test as in Example 1. The results are shown in Table 2.

[0022]

[Table 1]

As is clear from Table 2, in the magnet samples 12 to 16 having a Zn content of 3 to 30% according to the present invention,
A high residual magnetic flux density Br of 6000 G or more is obtained and an excellent coercive force iHc is obtained. On the other hand, the comparative sample 11 containing a small amount of Zn was poor in magnetic properties and was insufficient in strength required as a magnet. In addition, Comparative Example Sample 1
In No. 7, since the Zn content is excessive, the residual magnetic flux density Br is lower than the others.

Example 4 10 wt% of zinc powder was added to each of the nitriding powder having an average particle size of 50 μm produced in Example 1 and the powder obtained by further pulverizing this powder to 3 μm, and mixed by a ball mill. The mixed powder is applied with a magnetic field of 15 kOe for 4-10 Ton
It was compression molded at a pressure of / cm ² . Then, the molded body was charged into an electric furnace and heat-treated at 500 ° C. for 2 hours in an argon gas atmosphere to obtain a plurality of magnet body samples, and the magnetic characteristics of these magnet body samples were measured by a BH tracer.

FIG. 3 shows the effects of the average powder particle size and the molding pressure on the maximum magnetic energy product BHmax and the magnet body density. As shown in the figure, a magnet body sample using 50 μm coarse powder has a high density even in relatively low pressure molding, and has excellent magnetic characteristics of BHmax 10 MGOe or more at a molding pressure of 4 ton / cm ² or more. It became clear that it is more suitable for production than it is used.

Example 5 Neodymium having a purity of 99% or more, electrolytic iron, cobalt, and T
i or Mo is mixed in a predetermined ratio and dissolved to dissolve Th Mn ₁₂
Nd Fe ₉ Co ₂ Ti to a compound of type crystal structure as the main phase,
It was produced alloy ingots of Nd Fe ₉ Co ₂ Mo composition. This was homogenized at 1200 ° C. for 12 hours in an argon gas atmosphere, and then pulverized by a stamp mill and a ball mill to obtain a mother alloy powder having an average particle size of 30 μm. Next, this mother alloy powder was kept at 30 ° C. in nitrogen gas at 360 ° C. for 16 hours to infiltrate N and obtain a nitride powder. Subsequently the powder nitride, the powder was further pulverized into until 3 [mu] m, the particle diameter of 5 [mu] m Zn powder was added and mixed 10% by weight, of the 5 Ton / cm ² while the mixed powder by applying a magnetic field of 15 kOe It was compression molded with pressure. After that, the molded body was charged into an electric furnace and heat-treated at 375 ° C. for 6 hours in an argon gas atmosphere to manufacture magnet body samples 21 to 24.
It was subjected to the same measurement test of magnetic properties as in. The results are shown in Table 3.

[0027]

[Table 3]

As is apparent from Table 3, the present invention
The magnet samples 22 and 24 using the coarse powder of 30 μm have excellent magnetic characteristics (BHmax) regardless of the alloy type, as compared with the magnet samples 21 and 23 using the fine powder of 3 μm.

Example 6 An alloy ingot of Sm ₂ Fe ₁₇ composition was prepared from samarium and electrolytic iron in the same manner as in Example 1, and homogenized, crushed and nitrided to perform nitriding with an average particle size of 25 μm. A powder was obtained. To this powder, 6 wt% of Sn powder was added and mixed,
After compression molding in a magnetic field at a pressure of 5 Ton / cm ² , heat treatment was performed in an electric furnace in a temperature range of 100 to 700 ° C. for 4 hours to obtain a plurality of magnet body samples. The magnetic properties were measured by BH tracer.

FIG. 4 shows the effect of the heat treatment temperature on the coercive force iHc of the magnet sample. From the figure, the coercive force iHc peaks at a heat treatment temperature of around 350 ° C.
It has been revealed that an excellent coercive force iHc of 2500 Oe or more can be obtained in the temperature range of 100 to 600 ° C. The surface of the magnet sample that had been heat treated at 700 ° C had Sn
A part of the melting trace of was found.

Example 7 Example. Sm ₂ (Fe _0.9 C manufactured in the same manner as in No. 1)
o _0.1 ) ₁₇ N ₃ powder with an average particle size of 25 μm,
5 wt% of Sn-Zn alloy powder was added and mixed. This mixed powder was applied with a magnetic field of 15 kOe on one side and 5 Ton /
After compression molding with a pressure of cm ² , put it in an electric furnace and
Heat treatment was performed at 4 ° C. for 4 hours to obtain a magnet body sample 31. On the other hand, the molding die was heated to 350 ° C., and while applying a magnetic field of 15 kOe in the same manner, warm compression molding was performed at a pressure of 2 Ton / cm ² for 5 minutes to obtain a magnet body sample 32. The magnetic characteristics (BHmax) of the obtained magnet samples 31 and 32 are 13.3 M each.
It was found that GOe was 13.7 MGOe, and the heat treatment, which is a requirement of the present invention, can be omitted by performing warm forming.

[0032]

As described above in detail, according to the method for producing a rare earth bonded magnet according to the present invention, the average powder particle size is obtained by combining the low melting point metal or alloy with the alloy powder and the subsequent heat treatment. Can produce magnets with excellent magnetic properties even when using a coarse powder of 20 to 150 μm, the need for compression molding at high pressure is eliminated, and mold life is extended.
A significant improvement in manufacturability can be achieved. Further, since the coarse powder is used, the oxidation of the powder can be suppressed, and the durability reliability of the obtained magnet body is significantly improved.

[Brief description of drawings]

FIG. 1 shows the maximum magnetic energy product BHmax of a magnet sample,
It is a graph which shows the influence of the average particle diameter of alloy powder on coercive force iHc and residual magnetic flux density Br.

FIG. 2 is a graph showing the effect of average powder particle size and holding time on the increase in the weight of oxidized alloy powder.

FIG. 3 is a graph showing the effects of average powder particle size and molding pressure on maximum magnetic energy product BHmax and magnet body density.

FIG. 4 is a graph showing the effect of heat treatment temperature on coercive force iHc.

Claims (2)

[Claims] 1. An alloy powder having a rare earth metal (R), Fe and N as main components and a compound having a Th ₂ Zn ₁₇ or Th Mn ₁₂ type crystal structure as a main phase and having an average particle size of 20 to 150 μm and Sn. , Zn, Pb, In, Al and Mg are mixed in an amount of 3 to 30% by weight, the mixed powder is compression-molded and then heat-treated at a temperature range of 100 to 600 ° C. A method of manufacturing a rare earth bonded magnet. 2. The method for producing a rare earth bonded magnet according to claim 1, wherein the compression molding is performed at 100 to 600 ° C. and the subsequent heat treatment is omitted.